A typical motor vehicle is generally characterized as comprising an unsprung mass and a sprung mass. The unsprung mass generally consists of all of the parts of the vehicle not supported by the vehicle suspension system such as the tire/wheel assembly, steering knuckles, brakes and axles. The sprung mass, conversely is all of the parts of the vehicle supported by the vehicle suspension system. The unsprung mass can be susceptible to disturbances and vibration from a variety of sources such as worn joints, misalignment of the wheel, brake drag, irregular tire wear, etc. Because vehicular tires support the sprung mass of a vehicle on a road surface and such tires are resilient, any irregularities in the uniformity or dimensions of the tire, any dimensional irregularities in the wheel rim, and/or any dynamic imbalance or misalignment of the tire/wheel assembly will cause disturbances and vibrations to be transmitted to the sprung mass of the vehicle thereby producing an undesirable or rough vehicle ride, as well as reducing handling and stability characteristics of the vehicle. Severe vibration can result in dangerous conditions such as wheel tramp or hop and wheel shimmy (shaking side-to-side).
It is now standard practice to reduce some of these adverse vibrational effects by balancing the wheel rim and tire assembly by using a balance machine and clip-on lead weights. The lead balance weights are placed on the rim flange of the wheel and clamped in place in a proper position as directed by the balancing machine. The balancing procedure can reduce imbalance in the tire/wheel assembly, however, perfect balance is rarely achieved. Balancing is not an exact art and the results are dependent upon the specific set up of a tire/wheel assembly on a specific balancer at that moment in time. Balancing is an improvement and will reduce the vibration of the tire/wheel assembly in comparison to an unbalanced tire/wheel assembly. However, even perfect balancing of the tire/wheel assembly does not necessarily mean that the tire will roll smoothly. The balancing of the tire/wheel assembly must necessarily be done in an unloaded condition. When the balanced tire is placed on the vehicle, the weight of the vehicle acts on the tire through the interface or contact area of the tire and the road surface which is commonly known as the tire footprint. Irregularities in the tire are common such that even a perfectly balanced tire can have severe vibrations due to non-uniformities in the tire which result in unequal forces within the tire footprint.
A level of non-uniformity is inherent in all tires. In the art of manufacturing pneumatic tires, rubber flow in the mold or minor differences in the dimensions of the belts, beads, liners, treads, plies of rubberized cords or the like, sometimes cause non-uniformities in the final tire. When non-uniformities are of sufficient magnitude, they will cause force variations on a surface, such as a road, against which the tires roll and thereby produce vibrational and acoustical disturbances in the vehicle upon which the tires are mounted. Regardless of the cause of the force variations, when such variations exceed the acceptable minimum level, the ride of a vehicle utilizing such tires will be adversely affected.
Balancing of the tires has also been accomplished by using methods other than balance machines and lead weights. For example, Fogal in U.S. Pat. No. 5,073,217 disclosed a method of balancing a vehicle tire/wheel assembly by introducing a pulverulent synthetic plastic material into the interior chamber of the tire wheel assembly. The pulverulent synthetic plastic material has the added effect of compensating for the radial and lateral force variations generated at the tire road interface. The movement of the pulverulent synthetic plastic material within the tire is proportional to the downward force of the vehicle weight and the centrifugal force due to the tire rotation. Also, it has been found for some tire/wheel assemblies, particularly for use with passenger vehicles, a combination of lead weight balancing or the like with the addition of a predetermined amount of material introduced into the tire/wheel assembly to compensate for radial and lateral force variations at the tire/road footprint of a pneumatic tire of a vehicle. Such disturbances are due to tire/wheel assembly imbalance, non-uniformity of the tire, temporary disturbances in the road surface, or other vibrational effects of the unsprung mass of a vehicle. The applicant's concurrently filed, co-pending U.S. patent application Ser. No. 09/405,521 entitled Method for Equalizing Balancing Radial and Lateral Force Variations at the Tire/Road Footprint of a Pneumatic Tire, which is hereby incorporated by reference describes such an approach to disturbance compensation. This approach is briefly described with reference to prior art FIG. 4 which illustrates the innumerable radial impact forces (Fn) which continuously react between the road R and the tread T at the lower portion or footprint B during tire/wheel assembly rotation. There are an infinite number of such forces Fn at virtually an infinite number of locations (Pn) across the lateral width W and the length L of the footprint B, and FIG. 4 diagrammatically illustrate five such impact forces F1-F5 at respective locations P1-P5. It is assumed that the forces F1-F5 are different from each other because of such factors as tire wear at the specific impact force location, the road condition at each impact force location, the load upon each tire/wheel assembly, etc. Thus, the least impact force is the force F1 at location P1 whereas the greatest impact force is the force F2 at location P2. Once again, these forces F1-F5 are merely exemplary of innumerable/infinite forces laterally across the tire 11 between the sidewalls SW1 and SW2 and circumferentially along the tire interior I which are created continuously and which vary as the tirelwheel assembly 10 rotates.
As these impact forces are generated during tire/wheel assembly rotation, the material 20 is adapted to relocate in dependency upon the location and the severity of the impact forces Fn. In the preferred embodiment, material 20 is a composition of dry, solid particles, wherein relocation of the particle mixture 20 through movement of the individual granules, powder and dust is also inversely related to the magnitude of the impact forces. For example, the greatest force F1 is at position P1, and due to these greater forces F1, the particle mixture 20 is forced away from the point P1 with the least amount of the particle mixture remaining at the point P1 because the load force there is the highest. Contrarily, the impact force F is the lowest at the impact force location point P2 and therefor more of the particle mixture 20 will remain there. In other words, at points of maximum or greatest impact forces (F1 in the example), the quantity of the particle mixture 20 is the least, whereas at points of minimum force impact (point P2 in the example), the quantity of particle mixture 20 is proportionately increased. This movement of material creates lift, thereby substantially equalizing the radial and lateral force variations. Accordingly, the vibrations or impact forces Fn force the particle mixture 20 to continuously move away from the higher or excessive impact areas F1 or areas of maximum imbalance F1 and toward the areas of minimum impact forces or imbalance F2. The particle mixture 20 is moved by these impact forces Fn both laterally and circumferentially, but if a single force and a single granule of the particle mixture 20 could be isolated, so to speak, from the standpoint of cause and effect, a single granule located at a point of maximum impact force Fn would be theoretically moved 180 degrees therefrom. Essentially, with an adequate quantity of particle mixture 20, the variable forces Fn create through the impact thereof a lifting effect within the tire interior I which equalizes the radial force variation applied against the footprint until there is a total force equalization circumferentially and laterally of the complete tire/wheel assembly 10. Thus the rolling forces created by the rotation of the tire/wheel assembly 10 in effect create the energy or force Fn which is utilized to locate the particle mixture 20 to achieve lift and force equalization and assure a smooth ride. Furthermore, due to the characteristics of the particle mixture 20, road resonance is absorbed as the tire/wheel assemblies 10 rotate.
While the use of a compensating material introduced into the interior of the tire has been found to work effectively, either alone or in combination with other balancing techniques, a limitation has been found in how to introduce this material into the tire. In the prior approaches, as depicted in FIG. 3, pulverulent material 20 deposited in mound M is suspended in an air stream and introduced into a tire through a hose line (not shown) and valve stem 14 of tire valve 13 used for inflation of tire 11. Although such an approach works sufficiently, this method of delivery of a compensating material is in some instances an inconvenient delivery method, and may result in contamination of a work place where a wheel assembly is being balanced. This delivery system has further been utilized in the aftermarket environment to facilitate balancing of replacement tires, and no effective approach to introducing such material into a tire/wheel assembly at original manufacture has been provided.
There is therefore a need for an improved method and system for delivery of a compensating material into the interior of a tire, in a simple and effective manner.